Receiver of electrical impulses.



F. K. VREELANDQ RECEIVER OF ELECTRICAL IMPULSE-S.

APPIIICATION TIL ED JAN. 2; 1907- Patented Sept 2 SHEEIS-SHEET I.

1 Witnesss F. K. VREELAND. RECEIVER OF ELECTRICAL IMPULSES. APPLICATION FILED mu. 2. 1901.

Patented Sept. 11, 191?.

2 SHEETS-SHEET 2- In; Ven tor M 24 Attorneys.

lFREDEBICK K. 'VREELAND, 0F MONTCLAIR,

NEW JERSEY, ASSIGNOR TO VREELAND APPARATUS COMPANY, INC., 0]? NEW YORK, N. Y., A CORPORATION OF NEW YORK.

RECEIVER OF ELECTRICAL IMPULSES.

Specification of Letters Patent. Patgntggdl Sept, 1111, 1191?,

Application filed January 2, 1907. Serial No. 350,476.

'1 '0 all whom it may concern:

Be it known that I, FREDERICK K. Vnnn- LAND, a citizen of the United States, residing at Montclair, in the county of Essex and State of New Jersey, have invented a certain new and useful Improvement in Re ceivers of Electrical Impulses, of -Which the following is a description.

4 This invention relates to the detection and observation of Wireless telegraph or other signals of a sustained or continuous character, and particularly'to the reception of signals produced by an undamped oscillator.

The signals produced by an ordinary spark transmitter are intermittent in character and consist in adamped wave trains following each other in rapid succession and separated intervals of inactivity. The class of signal impulses to which this invention relates particularly are preferably undamped oscillations of constant intensity which are broken up into signal impulses by interrupting the wave train, by varying its frequency, or otherwise altering its character. Instead of an absolutely undamped oscillation it is possible to use an oscillation of somewhat varying intensity provided this is suflicientlv sustained to have a reasonably constant elfect upon the receiving apparatus during a sufliciently large number of successive oscillations.

Such sustained oscillations possess peculiar advantages for wireless signaling which it is the-purpose of this invention to utilize.

The invention comprises several functions: (1) The b eaking up of the continuous or sustained signal'impulse into an intermittent or pulsating one which is readily observed in a telephonic receiver. This is accomplished by causingthe signal impulses to produce beats by interference with a locally generated sustained oscillation whose frequency is slightly different from that of the signal impulses. (2) A peculiarly sensithe method of selective signaling resulting from the fact that the beat frequency of the observed signals is dependent on the difference in frequencies of transmitter and receiver. Hence a very small variation in the former will produce a relatively large variation in the beat frequency. 3) It provides a means of utilizing an elect-romechanical receiver whose sensitiveness is greatly increased by means of the locally generated oscillation.

produce a click at the series of strongly,

The signal produced by an undamped oscillator or other generator of practically continuous sustained oscillations is not suited to observation by ordinary telephonic receivers.

a given signal impulse is practically continuous and constant in intensity its efi'ect upon the telephonic receiver is simply to beginning and a click at the end of the impulse; these clicks being inconspicuous and diflicult to observe. Various methods have been proposed for breaking up such a signal into an intermittent or'vibratory impulse; for example, by inserting a mechanical interrupter in the telephone circuit, thus producing a plainly audible buz'z. In the invention herein described this is accomplished by combining the sustained or unclamped signal oscillations with simi lar undamped or sustained oscillations of slightly different frequency'generated at the receiving station, producing a difi'erential or beat frequency.

Any suitable form of electrical oscillator producing sustained high frequency oscillations may be employed for the signal and local oscillators, such, for example, as the oscillator described in my Patent No. 829934.

The interference of the oscillations Will produce beats similar to those which occur when two slightly diiferent musical notes are sounded together; that is, there will be intervals of maximum activity when the two tro-mechanical detector. Such detectors are cumulative in their action and capable of storing up the energy of a succession of high frequency oscillations into a single uni-directional impulse, Such detectors however as ordinarily used are rather insensitive and ill adapted for the detection of feeble sig nal impulses. Their sensitiveness can be be accomplished greatly increased, however, by superimposing the feeble signal impulse on a locally generated current of greater intensity.

\Vhere the signal impulses are of such high frequency that the telephone diaphragm or other moving part of the electromechanical receiver cannot respond to their individual oscillations, the locally generated current with which they are combined must also be an alternating current. If this alternating current is of exactly the same frequency and in synchronism with the signal impulses the resultant mechanical effect Will be a uni-directional force whose magnitude is proportional to the product of the electromotive force or intensity of the signal current and the electromotive force or intensity of the locally generated current. Hence by employing a strong local current or electromotive force the sensitiveness of the receiver of feeble signal impulses is greatly increased. If the two oscillations have not exactly the same frequencythis amplifying etfect will he intermittent and the resulting signal will he an interrupted or periodic one as in the case where the two oscillations of nearly equal intensity were caused to produce surges or heats by interference in a common oscillating circuit.

This production of beats affords a peculiarly delicate means of discriminating between signal impulses of nearly the same frequency. The frequency of the beats or surges depends upon the difference of frequencies of the signal impulse and of the locally generated oscillation. Hence a very slight variation in the former will produce a correspondingly large variation in the differential or beat frequency. Thus two sending stations whose frequencies are so nearly the same that ordinary methods of tuning would not discriminate between them may be readily distinguished from each other by the comparatively large difference in pitch of the note produced by the beats. If this note is of audible frequency, the discrimination may be made by the ear, or it may be made automatically by mechanically tuning the receiver to respond to a definite beat frequency by any of the well known methods.

In the accompanying drawings, Figure 1 is a sectional view illustrating an electro-.

static telephone, this being one form of apparatus which may be-used. in carrying out the invention; Fig. 2 is a similar view of a disk form of magnetic apparatus: Figs. 3.

4 are diagrams illustrating the principle of the amplifying device; Figs. 5. (i, 7 are diatelegraph); and Figs. 8 and 9 are diagrams illustrating one feature of the invention carried out with a polariphone detector.

The detector may he an electrostatic telephone receiver, such as shown in Fig. l. in which 1 is a flexihle diaphragm preferably of glass, celluloid or other elastic insulating It, and arranged so that its distance from the diaphragm may be regulated by means of the screw 3. These parts are mounted in a holder 4 of an ordinary telephone receiver.

The metallic coating of the diaphragm is preferably on the side of the diaphragm away. from the opposing metallic disk 2 so that the insulating material of the diaphragm aids in preventing leakage or spark discharges which might otherwise occur. and makes it possible to bring the diaphragm and disk close together- The high dielectric constant ofthe diaphragm also tends to increase the mechanical force. The conducting coating of the diaphragm constitutes one terminal of the apparatus and the adjustable metallic disk'constitutes the other terminal. these terminals being led to hind ing posts 5, 6 on the holder 4. The corresponding -magnetic form of instrument is illustrated in Fig. 2, in which 7 and 9 are two coils of tine wire or thin metallic rihhon wound spirally in disk form and placed side by side and close together. One of these coils 7 is attached to a flexible diaphragm 9 of elastic insulating material, which is mounted in the holder 10 of an ordinary telephone receiver.. The second coil 8 is fixed rigidly to an adjustable insulating support 11. The coils 7 and 8 may be connected either in series or in parallel and they may he wound in the same direction so as to attract each other, or in opposite directions so as to repel each other when traversed in series or parallel by an electric current.

the two charged surfaces should be prefertuning. With the magnetic form the forceispractically independent of the distance between the coils. if this distanceis small compared to their diameter, hence very close proximity of the coils is not so important. except when a non-inductive winding is nausea used. These .receivers would not be sufliciently sensitive to detect the feeblest signal impulses without the employment of the amplifying device which constitutes a part of my invention.

The principle of this amplifying device is represented in connection with theelectrostatic telephone receiver in Fig. 3, in which 1 and 2 represent the opposing surfaces of the receiver; 16, 17 represent the circuit through which the feeble impulses are received; 18 is a battery or other source of electrical energy for giving the lates 1, 2 a high-voltage initial charge. T is battery is shunted around theplates 1, 2'; choke coils 19, 20, may be employed to prevent the feeble impulses from passing through the battery circuit, although these can be omitted if the battery circuit is opened at 20 the switch 21 at the time the signal impulses are being received. 1 Condensers 23, 21 are placed in the signal circuit 16, 17, to prevent the battery current. from passing through the signal. circuit. Where the condensers may also be utilized for holding the charge supplied by the battery 18 and replenishing that of the detector 1, 2 as it becomes dissipated by leakage or otherwise. The capacity of the condensers 23, 24 is preferably much larger than that of the detector 1, 2. The force exerted by the ele ments 1, 2, upon each other is proportional to the square of the difference of potential between these elements. Thus, if v be of small electromotive force to be detected, the attraction between the two elements of the system will be proportional to if. If now the system be given aninitial charge at a high potential V, and the small voltage to be indicated, 11, be added to this, the increase due to o in the force between the two elements, that is, the force available for actuating the diaphragm, will be very much greater than the force due to the voltage '0 alone. The amount of the'increase in sensitiveness depends upon the ratio of the initial voltage V to the voltage a to be indicated. Thus, if'the force due to V alone is equal to V when the voltage is now increased to V-l-o, the. force between the two elements becomes The increase in the force due to the addition of 'v to V-is thus 2Vo+ u of if V is large relative to o it is approximately 2V0.

This fraction represents the amount by which the sensitiveness of the instrument current, and condensers 23, 24, being switch 21 is opened during signaling these has been increased. The source of energy 18 may be one having a volta e many times that of the signal impulses. n the case of an electrostatic telephone detector this charging voltage may properly be from 200 m to 500 volts, or even higher, if the apparatus is properly constructed and insulated.

The same amplifying principle is applicable to the magnetic telephone detector, the principle of which is illustrated in Fig. 4, 5 in which the disk coils 7, 8, are connected in circuit with a battery or other source of electrical energy 18. The signal circuit 16, 17, is connected with these coils, a choke coil 19 being provided to prevent the signal impulses from shunting the disk coils 7 8, while permitting the flow of the exciting used to' prevent-the current of the battery 18 from passing through the signal. circuit. 5 Or the choke coil and condensers may be omitted and the exciting current allowed to pass through this signal circuit, if this is continuous.

The theory of this form of receiver is similar to that of the electrostatic form. The attraction or repulsion exerted on each other by the coils 7, 8 is proportional to the square of the current flowing therein (or if the coils are connected in parallel and the current is not equally divided between them, the force is proportional to the product of the currents in the two coils). Hence, the variation in the steady force due to the constant exciting current caused by the superposition on it of the small signal current is proportional, not to the square of the signal current, but to twice the product of the signal current by the exciting current. The degree of amplification is thus twice the ratio of the exciting current to the signal current, as in the case of the electrostatic receiver the degree of amplifi cation was proportional to twice the ratio of the exciting volt-age to the signal voltage.

Although I have described the telephonic form of receiver as being that to which this invention is most readily applicable, it may be embodied in many other forms; for example. the moving element or elements instead of being mounted in a diaphragm may be suspended in any suitable way, with means .for observing the motion or force due to the mutual action of the two elements. The amplifying device will then serve to increase this force or'motion in the same manner that it increases the sound in the telephone.

Receiversof either the electrostatic or magnetic types above described may be used in the reception of ordinary telephonic cur- 1m; rents, in which case they constitute very eflicient and sensitive recei vers. The diaphragm responds to each individual variation in the signal impulses,thus produclng a motion of the diaphragm correspondmg to the va- 1530 riations of the voice currents. Either form of receiver, however, may be used for detecting currents of such high frequency that the ordinary teleprone diaphragm, on account of its sluggishness, is incapable of responding to the individual variatlonsr This is accomplished by causing the diaphragm to respond, not to each individual variation or alternation of the signal current, but to the force due to a succession or group of these alternations. In either the electrostatic or the disk-form magnetic telephone the force between the elements is always an attraction or alaways a repulsion whatever the direc tion of the signal current, at least in those elements at once; ,Thus, a rapidly alternating impulse will result in a unidirectional though intermittenti pull or push on the diaphragm. If the frequency be sufliciently high the pull may be regarded as continusignal impulse tends to increase the initial charge or current it will increase the force, andwhen it tends-to decrease the charge or current it will decrease the force, and the resultanfleffects of an alternating impulse Q will be no greater than if the exciting charge or current were not applied. If, however, the exciting charge or current is alternating with the same frequency as the signal impulses and in synchronism with these impulses, then the superposition of the signal impulse upon it will always increase or always diminish the force between the rela- I tively moving elements whatever the direction of the impulse; the am lification is thus the same as in the case 0 currents of low frequency. 1 f

It is diflicult in practice to produce high frequency currents exactly in synchronism with the signal impulses, but fortunately this is not necessary or even desirable in most cases. If there is a slight difference of frequency between the two oscillations there will be certain periods when they are in synchronism or opposition and the amplification occurs, and other periods when they are in quadrature and there is no am plification. The result will be a periodic force'acting on the diaphragm, producing beats whose frequency depends upon the difference in frequency of the two oscillations.

tinuou sly audible note in the telephone. The pitch of this audible note may be varied at will by varying the frequency of the local I cycles per second, which is/a high pitche forms in whlch the current reverses in both musical note. If the frequency of the local oscillator differs from that of the signal impulses by only one-tenth of oneper cent. the

' frequency of the beats will be one hundred cycles per second which will produce a low itched note. In general the beat frequency 1s equal to the difference between the frequencies of the signal impulses and the local oscillations. I

In Fig. 5 the electrostatic receiver is shown applied to a wireless telegraph system. 25 is the antenna or collecting circuit,

"A resonant circuit R S S is coupled with the collecting circuit and comprises the electrostatic receiver R, the secondary S of the transformer coupling the resonant c1rcuitto the antenna clrcuit, and'a second coil.

S, which is inductively coupled to the local oscillator. The coupling of this second coil to the oscillator need not be close; it is usually sufficient to have the oscillator simply operating in the same room as the resonant clrcuit, as the latter is exactly. or very nearly in tune with the oscillator. 'The resonant circuit is tuned to the signal impulses by adjusting the capacity of the receiver R (for example by re lating the distance between the plates) or y varying the inductance of the circuit, as by varying the self induction of one of the coils S S. i

Apeculiar advantage of both forms of electromechanical detector, but especially of the electrostatic form, is the fact that they .do not impose a large resistance or other cause of stray energy losses on the resonant circuit. The ener absorbed is almost wholly converted into mechanical work.'

Hence, such a detectormay be inserted di-' 7 rectly in the resonant circuit, so as to be "I I form of'this oscillator represented by O be- Thus, a long sustained signal im ulse, which ing shown in Fig. 5. The frequency of phone only as a click at the beginningdand a click at the end of the signal, is now would ordinarily be observed in the teleroken up mtoa vibratory force whlch gives a consuch an oscillator is very easily controlled by' varying the capacity or'inductance of the aeeaeea 'synchronism with the signal impulses or caused to pr duce beats of any desired frequency.

Such a system is selective by virtue of the resonance of the tuned circuit R S S to the signal oscillations, but a further degree of selectivity may be attained by mechanically" as the natural frequency of the telephone.

In this manner an exceedingly high degree of selectivity may be attained, for, as the frequency of the beats depends upon the dif-' ference of frequencies of the signal impulses and of thelocal oscillator, the slightest variation in either will produce a large change in the frequency of the beats.

An additional element of selectivity may be secured in the case of the electrostatic-receiver in the following manner: The diaphragm of the receiver is made relatively flexible in order that it may have a comparatively large amplitude of vibration, and is tuned mechanically by loading it so that it will vibrate at a definite frequency. As I the natural frequency of the resonant circuit R S S depends upon the capacity of the receiver R and as this capacity depends upon the distance between the diaphragm and the fixed plate, it is evident that the motion of the diaphragm will vary the natural frequency of this circuit by varying the capacity of the receiver. If, for example, the resonant circuit is tuned to the same frequency as the signahimpulses when the diaphragm is in its mean position, the attraction of the diaphragm toward the fixed plate will cause the capacity of the receiver to increase, the natural frequency of the-circuit will be diminished, and'the circuit will cease to resonate to the signal impulses. The diaphragm will then return to its initial position. If now the signal impulses be made intermittent with a group frequency equal to the mechanical frequency of the receiver diaphragm, then the return of the dlaphra'gm to its starting point (which corresponds to resonance in the receiving circuit) will occurat the moment when a second impulse is received from the transmitting station, and this impulse will give an additional impetus to' the diaphragm. If, however, thegroup' frequency of the signal impulses is different from that of the diaphragm, a second impulse will occur at a time when the diaphragm is displaced from its former position and the resonant circuit. is out of tune with the sig nal impulse, andno additional or only a slight additional impetus will be given to the diaphragm.

Fig. 6- represents a somewhat difierent arrangement of the two oscillatin circuits from that illustrated in Fig. 5. ere the antenna 25 is coupled to the oscillatingcircuit S R L G which comprises the secondary S of the transformer, the electrostatic receiver R, the inductance L, and a condenser G Whose capacity is large compared to that of the receiver R. This condenser serves as the coupling between the oscillating circuit S R L G which is tuned to the frequency of the signal impulses, and the local oscillating circuit C,C S. ,L which is tuned to the frequency of the local oscillator, which is preferably slightly different from that of the signal impulses. This local oscillating circuit is coupled to the oscillator through a transformer P S,. This transformer may be loosely coupled, as in the case illustrated in Fig. 5, or it may be closely coupled so as to produce a large current in the oscillating circuit QC S L These oscillations will, however, induce only n10derately strong forced oscillations in the receiver circuit S R L 0,, owing to the two cir cuits being slightly out of tune, and the intensity of these exciting oscillations may be varied at will by altering the capacity of the condenser 0 and so controlling the closeness of the coupling between the two oscillating circuits. Obviously, a great variety of other arrangements may be employed for applying the signal impulses and the local exciting oscillations to the receiver.

Fig. '7 represents an arrangement similar to that of Fig. 5 in which the magnetic receiver is substituted for the electrostatic re ceiver. In this case it is necessary to insert a condenser C in the resonant circuit R S G S .for the purpose of tuning.

ing by tuning the receiver to the wave frequency, the sharpness of the resonance depends upon the looseness of the coupling between the antenna and the resonant circuits. I. A closely coupled system is not sharply selective, While a loosely coupled one gives resonant currents of a feeble intensity.

The conditions of sharp selectivity and intense resonance are mutually opposed and a compromise is necessary. The result, where selective tuning is required, 'is a loosely coupled, system giving. signals of relatively feeble intensity. Where the beat receiver is used, involving the principle of differential frequencies as herein described, this com'-' promise is not required. The apparatus not being dependent upon resonance for selectector with a cdrresponding increase of sensitiveness. If by virtue of the close cou* pling signals of undesired frequencies succeed in entering the oscillating circuit, they are sifted out because of their failure to produce beats of suitable frequency with the local oscillations. The importance of this feature in extending the rangeof selective signaling is evident.

The method of breaking up a'continuous or undamped signal impulse into an intermittent one by causing it to produce beats with the current from a local generator of continuous oscillations slightly out of tune.

with the signal impulses, may be applied to a great variety of detectors other than the electro-mechanical detectors herein described. For example, in Figs. 5 and 6 any suitabledetector of high frequency currents may be substituted for the elestrostatic detector R, and the beats resulting from the su'perposition of, the two sets of oscillations-ho the oscillating circuit will produce an mtermittent signal or note in the detector. If the detector is of a type which does not lend itself to the amplifyi principle herein described, the two sets 0 oscillations, '5. e., the (preferably) free oscillations due to the sig: nal impulses and the forced oscillations excited by the local source, should have the sameor nearly the same magnitude. In that case the current beats set u in the oscillating circuit will consist inmtervals of high activity separated by intervals of little or no activity. The detector will then receive a series of impulses coincident with the successive periods of activity. The resulting note may becontrolled by varying the frequency ofthe local generator, and the system of 'mechanical tuning to this note maFy beapplied as set forth above. 45 A I 0 r example, Fig. 8 shows an arrahgement in which the polariphone detector is used. The resonant circuit S L C S is coupled to the antenna or collecting circuit through .the transformer P S, and to the oscillator through the transformer P S. The polariphone detector R, with its associated apparatus, is shunted across a portion of the circuit where it is subjected to' a high potential difference without impos ing its high resistance in the path of the oscillations. It is thus affected by the beats resulting from the superposition of the two sets of oscillations in the resonant circuit.

Fig. 9 represents an arrangement similar to that of Fig. 11 in which a system of electrical tuning to the beat frequencies is substituted for the mechanical tuning. The local circuit of the polariphone R is coupled through a transformer to an oscillating circuit tuned electrically to the frequency of set Lassa th beats, and including the telephone or other indicatin device. Or both electrical and mechanica tuning may be employed simultaneousl What I claim is:

1. A receiver ofsustained high frequency signal impulses, wherein are combined a detector, a localsource of sustained alternating currents of slightly different frequency from the signal impulses and means for combining the local currents-with the signal impulses andapplying the resultant beat current to the detector, substantially as set,

forth. I

2. A receiver of sustained high frequency signal impulses, wherein are combined a detector, a local source of sustained alternating currents of slightly different fre-.- quency from and greater intensity than the signal impulses and nfeans for combining the local currents with the signal impulses nating currents of slightly different frequency from the signal impulses, means for combining the local currents with the signal impulses and applying the resultant beat current to the detector, and means for selectivel ,ofiserving the beats, substantially as ort 1 4.: A receiver of sustained high frequency signal .impulses, wherein are combined a detector; a local source of sustained alternating currents of slightly different frequency from the signal impulses, means for combining the local currents with the signal impulses and (applying the resultant beat current to the detector, and means tuned to the beat frequency for selectively observing the beats, substantially as set forth.

-5. A- receiver of sustained high frequency signal, impulses, wherein are combined a" local circuit, means for impressingthe sigr' nal'impulses'upon suclf'circuit, a local source gofsustained' high frequency oscillationsof slightly different frequency fromthe signal impulses, means for. impressing these latter oscillations uponsuch local circuit so as thereby to be comblned with the'signal impulses and produce a resultant' beat current,

and a detector acted upon by. the'beat current and directly responsive thereto, substantially as set forth.

6. A receiver of sustained high frequency signal impulses, wherein are combined a. local circuit, means for impress ng the s1g'- nal impulses upon such c1rcu1t,a local sour e of sustained high frequency oscillations of slightly different frequency from the signal impulses, means for impressing these latter oscillations upon such local circuit so as impulses and produce a resultant beat our rent, and a detector in the local circuitand acted upon directly by and responsive to the beat current, substantially as set forth.

7. A receiver of sustained high frequency signal impulses wherein are combined a closed tuned oscillating circuit means for impressing the signal impulses upon such circuit, a local source ofsustained high frequency oscillations of slightly different frequency from the signal impulses, means for impressing these latter oscillations upon such oscillating circuit and means for observing variations in the'oscillations in said oscillating circuit, substantially as set forth.

8 A receiver of sustained high frequency signal impulses wherein are combined a closed oscillating circuit tuned to the frequency of the signal impulses, means for impressing the signal impulses upon said oscillating circuit,

a local source of sustained high frequency oscillations of slightly different-frequency from the signal impulses, whereby forced oscillations from the local source will be produced in said oscillating circuit and the signal impulses will be superimposed thereon, and means for observing the low frequency beats thereby produced in said oscillating circuit, substantially as set forth.

9. In a receiver of signal impulses, the combination with a detector comprising an electro-mechanical couple of relatively movable elements producing when excited an electrostatic field inwhich the elements mutually act on each other, of a local source of alternating currents separate from the signal current for exciting such couple,whereby the mechanical force exerted between the elements of the couple by the reception of the signal impulses will be modified, substantially as set forth.

10. In a receiver of high frequency signal impulses, the combination with a detector comprismg an electro-mechanical couple of relatively movable elements producing when excited an electrostatic field in which the elements mutually act on each other, of a local source of high frequency currents for exciting such couple separate from and of greater intensity than the signal impulses, whereby the mechanical force "exerted between the elements of the couple by the reception of the ,signal impulses will be amplified, substantially as set forth.

11. :Ina receiver of high frequencysignal impulses, the combination with a detector comprising an electro-mechanical couple of relatively-movable elements producing when excited an electrostatic field in which the elements mutually act on each other, of a local source of high frequency currents for exciting such couple-of slightly different frequency from the signal impulses, whereby the'electric couple will respond to the beats local source of high frequency currents for exciting such couple of slightly different frequency from the signal impulses, whereby produced and the mechanical force exerted the electric couple will respond to the beats produced andthe mechanical force exerted between the elements will be amplified, the receiver being .tuned to the beat frequency, substantially as set forth.

13. In a receiver of high frequency signal impulses, the combination with a detector comprising an electro-mechanical couple of relatively movable elements producing when excited an electrostatic field in which the elements mutually act on each other, of a local source of high frequency currents for exciting such couple, of greater intensity than. and of slightly different frequency from thesignal. impulses, whereby the electric couple will respond to the eats produced and the mechanical force exerted between the elements will be amplified, substantially as set forth.-

14. In a receiver of high frequency signal impulses, the combination with a detector comprising an electro-mechanical couple of relatively movable elements producing when excited an electrostatic field in which the elements mutually act on each other, of a local source of high frequency currents for exciting such couple, .of greater intensity than and of slightly different frequency from the signal impulses, whereby the elec-- tric couple will respond to the beats produced and the mechanical force exerted beexciting an electrostatic field in the telephone, such local-source being distinct from the source ofsignal currents, substantially as set forth. 3

16. Ina receiver of high frequency signal impulses, the combination with a detector comprising an electrostatic telephone, of

a local circuit including a source of high frequency currentsfor exciting an electrostatic field in' the telephone of. greater in tensity than the signal impulses, said local source being distinct from the source of signal currents, substantially as set forth.

17. In a receiver of high frequency signal impulses, the combination with a detector- 'forth.

com rising an electrostatic telephone, of a loca source of high frequency currents for exciting an electrostatic field in the telephone of slightly different frequency from the signal impulses, substantially as set 18. In a receiver rrf liigh' frequency signal impulses, the combination with a detector comprising an electrostatic telephone, of

a local source of high frequency currents for exciting an electrostatic field in the telephone of slightly different frequency from I the signal impulses, the receiver being tuned to the beat frequency, substantially as set 15- forth. I a

19. In a receiver ofhigh frequency signal impulses, the combination with -a detector comprising an electrostatic telephone, of a local source of-high Jrequency currents for exciting an electrostatic field the telephone of greater intensity thain and of -pulses, the combination of a tuned receiving ,circu1t an electrostatic detector included in vimpulses, substantially as set forth.

: exciting an electr slightly different frequency from the signal 20. In a receiver of high frequency signal impulses, the combination with a detector comprising, an electrostatic telephone, of, a local source of high frequency currents for atic field in the' telephone of greater intensity than and of slightly different frequency from the signal impulses, the receiver being tuned to the beat frequency, substantially as set forth.

21.. In a receiver of alternating signal impulse sfthe combination of a tuned receiving circuit an electrostatic detector and a local sourceof alternating current energy distinct from. the sourcerof the signal impulses for tfexciging the detector, substantially as set ort 22. In a receiver of alternating signal imand .-constituting the major part of the capaclty reactance ofsuch tuned receiving circuit and a local source of alternating current energy distinct from the source of the 3 signal impulses for exciting the detector,

substantially as set forth. i 23/.In a receiver of high frequencysignal I impulses, the combination of a tuned receiving circuit an electrostatic detector and a local source of high fre'queny currents dis-. tinct from the source of the signal impulses for (Exciting the detector, substantially as set ort 24. In a receiver of high frequency signal impulses, the combination of a tunedreceiving circuit an electrostatic detector included in and-constituting the major part of the capacity reactance of such tuned receiving circuit and a local source of high frequency currents distinct from the source of the signal impulses for exciting the detector, substantially as set forth.

25. In agreceiver of signal impulses, the combination of an antenna or collecting circuit, an oscillating circuit closely coupled thereto, adetector, a local source of oscillations and means where by the signal oscillations of the oscillating circuit and the local oscillations affect the detector simultaneously, substantially as set forth.

26. The method of detecting signal impulses, which consists in exciting an alterintensity, superimposing thereon the relatively feeble field excited-by the signal im pulses, and detecting the mechanical forces resulting from the superposition of these of large intensity and slightly difierent frequency compared with the signal impulsw,

superimposing thereon the relatively feeble field 'exclted by the signal impulses, and de-- tecting the beats resulting from the superposition. of these fields, substantially as set forth.

This specification signed and witnessed this twenty seventh day of December, 1906. FREDERICK K". VREELAN'D.

, Witnesses: 5N0. RoBT TA Jorm S. T471808.

sustained alternating nating electrostatic field of relatively large 

